The present invention is directed to improvements in valves, particularly butterfly-type valves, but is also applicable to ball valves and the like.
Butterfly valves and ball valves are provided with a movable valve member that rotates within a valve housing, about a diametral axis of the valve passage. In a butterfly valve, the movable valve element typically is in the form of a disc-like member provided on its outer peripheral surface with spherical contours forming a sealing surface. When the valve is fully open, the disc is oriented generally parallel to fluid flow through the passage. In a ball valve, the movable valve member has a generally spherical configuration and is provided with a large central opening. When the opening is aligned with the fluid passage, the valve is fully open. In the closed position, the spherical member is rated 90.degree. to completely block the passage.
Conventionally, a sealing element is provided to form a fluid tight seal between the valve body and the movable disc or ball, when the valve is in a closed position. Typically, the sealing element takes the form of an annular element, fixed in the valve housing in surrounding relation to the movable valving element.
In the William R. Hayes U.S. Pat. No. 4,676,481, assigned to White Consolidated Industries, Inc., there is shown a particularly advantageous form of annular sealing element for butterfly valves. The seal there disclosed is a so-called "soft seal", formed of durable plastic material. The patented seal is highly advantageous for a wide variety of applications. Nevertheless, for certain types of valve service, wherein the valve may be exposed to extremely high temperatures, for example, or to chemicals or solvents that might attack the plastic soft seal, it is advantageous to utilize a seal formed of metallic material. Metallic seals are, in general, well known, examples of such being the Scobie et al. U.S. Pat. No. 4,410,163 and the Barker et al. U.S. Pat. No. 4,487,216, for example. In certain cases, such as in the Barker et al. patent, for example, the metallic seal element functions primarily as a barrier to protect a soft seal. In the Scobie et al. patent, on the other hand, the metallic member is relied upon exclusively for sealing purposes.
In accordance with the present invention, an improved valve arrangement is provided which incorporates an advantageous form of thin metal annulus to provide a highly effective seal between the valve body and the butterfly disc or other movable element. The valve and seal arrangement of the invention incorporate certain unique features enabling highly efficient and reliable sealing to be achieved in a structure of simple and economical design.
In accordance with a specific aspect of the invention, the valve assembly includes a thin annular metal seal whose radially inner surface portions bear sealingly on the spherical outer surfaces of the butterfly disc. Pursuant to the invention, the configuration of the metallic seal element is such that the fluid pressure on the upstream side of the valve urges the inner portions of the seal in a closing direction against the surface of the butterfly disc. The configuration of the seal and of the valve housing, importantly is such that, as upstream pressures increase to the point of maximum desired stress in the thin metal sealing element, deflection of the element causes it to be supported in a region shifted radially inward from its original support, whereby the increased upstream pressure of the fluid may be effectively resisted without overstressing the material of the seal. The construction enables the seal to be of lightweight, flexible construction, so as to provide highly effective sealing even at low pressure differentials.
In accordance with another aspect of the invention, the construction of the valve and metallic seal is such that the seal relies only upon its own flexibility and the action of the pressure differential between the upstream and downstream sides of the valve for sealing effectiveness. It is neither necessary nor desirable to provide auxiliary devices, such as springs, annular tension windings, or the like to achieve reliable sealing contact. Rather, the design relies upon a relatively high degree of flexibility of the metallic seal element itself to establish an initial, low pressure seal. As the fluid pressure differential in the valve increases, the geometry of the valve and seal causes the fluid pressure to be applied to the seal, increasing its sealing effectiveness. The construction assures reliable and effective sealing, yet also minimizes wear on the relatively moving parts of the valve in the area of the seal.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.